Tagatose, an isomer of galactose, is low-calorie sweetener which is naturally produced. Although tagatose exhibits similar sweetness to sugar, that is, about 92% sweetness of sugar, tagatose is spotlighted as a sugar substitute since tagatose only has about 38% the calories of sugar and an about 4% the glycemic index (GI) of sugar.
Moreover, tagatose is an approved as Generally Recognized As Safe (GRAS) by the Food and Drug Administration (FDA) and thus permitted to be used as a sweetener for food, beverages, health food, diet additives and the like, and is known to have almost no side effects when ingested by humans and thus is anticipated to be widely used.
Methods for producing tagatose include a chemical method in which a chemical catalyst is used to isomerize galactose, and a biological method in which galactose is isomerized using an isomerase. Although the chemical method has advantages in terms of economic efficiency and yield, there are problems in that the chemical method requires chemical processes at high temperature and high pressure, has complicated processes, and causes industrial waste. Therefore, there is an increasing need for a biological method.
In the related art in relation to a technique for mass production of tagatose using an isomerase, Korean Patent No. 10-0872694 discloses a method for mass production of tagatose using an arabinose isomerase, and Korean Patent No. 10-0464061 discloses a method in which an isomerase is immobilized to an appropriate carrier, followed by introduction of galactose, thereby driving isomerization into tagatose.
However, since the biological method is more sensitive to reaction conditions than the chemical method, the biological method causes a great difference in process efficiency, final yield, and the like when the reaction conditions are adjusted. In addition, when using an isomerase immobilized to a carrier, properties of the prepared carrier and a degree of immobilization vary according to apparatuses used in immobilization and methods of immobilization, thereby making it difficult to determine process efficiency, production yield and the like, and obstructing active use of the biological method.
Therefore, there are needs for an apparatus for preparing enzyme-immobilized beads optimized for stable mass production of tagatose through the biological method, and for a method for effectively immobilizing an isomerase or microbial cells capable of producing the isomerase to a carrier.